1. Field of the Invention
This invention relates to an antenna, a watch provided with the antenna, and a method of manufacturing the antenna.
2. Description of the Related Art
A timepiece, which receives a radio wave including standard time information (hereinafter called a standard time radio wave) and corrects time automatically, has been used in recent years, and this kind of timepiece is called as a radio controlled timepiece. In Japan, two standard time radio wave stations transmit standard time radio waves in long waves of 40 kHz and 60 kHz.
Therefore, a radio controlled timepiece designed for use in Japan contains an antenna to receive the standard time radio waves of 40 kHz and/or 60 kHz.
Like ordinary timepieces, there are two types of radio controlled timepieces, one of which is a clock type including a table clock and a wall clock, and the other of which is a watch type including a wristwatch and a pocket watch.
The watch type radio controlled timepiece, which is very smaller than the clock type radio controlled timepiece, must use an antenna, which is very smaller than that used in the clock type radio controlled timepiece, for receiving the standard time radio waves. Further, if a case of the watch type radio controlled watch is made of metal such as titanium and stainless steel, the antenna used in the watch type radio controlled timepiece must be superior to that used in the clock type radio controlled watch in a radio wave receiving characteristic.
FIGS. 11 and 12 show a schematic longitudinal sectional view and plan view of two types of conventional antennas for receiving the standard time radio waves used in the watch type radio controlled time pieces.
The conventional antenna 51 for receiving the standard time radio waves shown in FIG. 11 is widely known by the Japanese Patent Application KOKAI Publication No. 2004-179803, and uses a laminated core 52 formed by laminating many amorphous soft magnetic alloy thin plates. On the laminated core 52, a coil 53 is wound between both end portions thereof. To increase the Q-value (ratio of output to input) indicating the receiving characteristic of the antenna 51, the laminated amorphous soft magnetic alloy thin plates are separated into two groups by spacers 54 in the laminating direction at both end portions of the laminated core 52.
The conventional antenna 61 for receiving the standard time radio waves shown in FIG. 12 is widely known by the Japanese Patent Application KOKAI Publication No. 2004-104551, and uses a laminated core 62 formed by laminating many amorphous soft magnetic alloy thin plates. On the laminated core 62, a coil 63 is wound between both end portions thereof. The conventional antenna 61 for receiving the standard time radio waves forms a closed loop by bending both end portions 65 of the laminated core 62 to come close to each other, in order to reduce a magnetic flux to leak to a metallic case 64 of a watch type radio controlled timepiece while the antenna is placed in the inside space of the metallic case 64.
In the conventional antenna 51 for receiving the standard time radio waves shown in FIG. 11, it is troublesome and requires much time to separate the laminated thin plates into desired two groups in the laminating direction at both end portions of the laminated core 52 by the spacers 54.
In the conventional antenna 61 for receiving the standard time radio waves shown in FIG. 12, the structure to form the laminated core 62 into the closed loop prevents the antenna 61 from being miniaturized.